1. Field of the Invention
The present invention relates to a cushion for placement in a shoe sole for cushioning and supporting a foot. More particularly, the invention relates to a plate support that has tubular portions disposed around a central portion for supporting a region of a foot.
2. Description of the Prior Art
FIG. 1 shows a sole employing a cushion 10 such as disclosed in U.S. Pat. No. 6,253,466, the disclosure of which in incorporated by reference herein. Cushion 10 is part of the midsole, but is partially exposed on its lower side and may contact the ground, thus serving also as an outsole.
The cushion has an outer tubular portion 24 that includes a medial tubular portion 18 and a lateral tubular portion 20, which are formed by resilient load-bearing tubular walls 19. Tubular portions 18 and 20 extend along medial and lateral edges of the foot shape of the sole. Tubular portions 18 and 20 extend generally along the medial and lateral edges of the heel shape part of the foot shape, in the heel region of the sole, opposite from each other with respect to the central portion 26. Tubular portions 18 and 20 also extend along the rear edge 22 of the heel shape, together forming the single, substantially continuous, outer tubular-portion 24. The resulting tubular portion 24 extends in a U-shape substantially continuously along the contour of the heel shape. Walls 19 forming the outer portion 24 are configured and dimensioned such that together with the main sole, walls 19 support edges of a foot and cushion impact produced thereon, for example, by walking, running, or jumping, without collapsing.
A hollow central portion 26 is disposed between and joined with the medial and lateral portions 18 and 20. Central portion 26 is formed by a resilient load-bearing central wall 28, which, as shown in FIG. 2, includes upper and lower wall portions. Central wall 28 is joined to the tubular walls 19 along a portion of its boundary 21, along the entire extent at which central portion 26 lies adjacent tubular portion 24, including on the medial, lateral, and rear sides of central portion 26. Bend sections 23 of the tubular portions 18 and 20 are bent along boundary 21 and have ends facing each other, which are connected. As seen in FIG. 1, bend sections 23 follow the shape of the boundary 21. Central wall 28 is configured and dimensioned for supporting and cushioning a central portion of the foot, in this case of the heel region of the foot, together with the main sole portion, without collapsing.
Cushion 10 also has recessed portions 30 that extend between the central and tubular portions 26 and 24. Recessed portions 30 join the central and tubular portions 26 and 24 while isolating vertical deformation between the sections of tubular walls 19 and central wall 28 that lie adjacent recessed portions 30.
As seen in FIG. 2, tubular walls 19 have vertically spaced elevated sections 32, and central wall has vertically spaced elevated sections 34. Because elevated portions 32 of tubular walls 19 are isolated from elevated portions 34 of central wall 28, substantially no vertical compression is transmitted therebetween across recessed portions 30.
Referring again to FIG. 1, cushion 10 also includes a coupling portion 36 with at least one wall elevated from the level of recessed portions 30, separating recessed portions 30 of cushion 10. Coupling wall 36 connects central elevated sections 34 to tubular elevated sections 32. This connection couples the adjacent elevated sections 32 and 34 such that vertical deformation is transmitted between tubular walls 19 and central wall 28.
Coupling portion 36 permits energy to be stored, absorbed, and returned to the foot by both central walls 28 and tubular walls 18 and 20 when cushion 10 is impacted in locations on either the central or tubular portions 26, 18, or 20 that are near coupling portion 36. Coupling portion 36 is disposed at the rear of the heel, generally aligned with a heel strike area 52.
It is well known in the art that during a step, particularly while a wearer is running, the wearer's foot strikes the sole generally along a strike path 66, shown in FIG. 1. The strike path 66 along the sole extends from the heel to the fore foot portion of the sole. This path 66 receives first and largest loads from impact on the sole.
The cushion is shown in FIG. 1 is disposed in the sole such that the heel strike area is disposed in the region defined behind lines 54 and 56. If cushion 10 is sized for a men's size 9.5 shoe, lines 54 and 56 intersect centerline 38 of cushion 10 at about 23 to 31 mm from the rear of cushion 10. Line 54 extends laterally at an angle 58 of about 25 degrees forward from a horizontal line 60 normal to the centerline 38. Line 56 extends medially at an angle 62 of about 5 degrees behind line 60. Thus, the coupling portion 36, being disposed generally centrally with respect to the heel strike area 52, is displaced laterally from the centerline 38.
Because central and tubular portions 26 and 24 are hollow, central portion 26 defines a central interior chamber 40, and tubular portion 24 defines a tubular interior chamber 42. Central interior chamber 40 extends substantially across the middle of the cushion. Central and tubular chambers 40 and 42 are communicated through the interior of coupling portion 36. Tubular and central walls 19 and 28 are coupled for transmitting vertical deformation therebetween where coupling portion 36 communicates interior chambers 40 and 42.
Central and tubular walls 28 and 19 also have stiffening ribs 44 that extend widthwise across central and tubular portions 26 and 24. As walls 19 and 28 of cushion 10 are of substantially uniform thickness, ribs 44 form grooves 46 on an opposite side of walls 19 and 28 therefrom. Ribs 44 increase the bending stiffness of walls 19 and 28.
As shown in FIG. 1, the bottom central wall 28 preferably includes an indented portion 64 that has substantially the same depth as ribs 44. Indented portion 64 may display decorative or trade insignia.
The cross-sectional shape of cushion 10 taken along plane II-II of FIG. 1, which extends widthwise and vertically through cushion 10, is best shown in FIG. 2. Both central and tubular walls 28 and 19 have an arcuate shape. Central wall 28 defines an oval cross-section.
The cross-sections of tubular walls 19 are generally circular when compared to the cross-section of central wall 28. Due to these shapes, cushion 10 stores and returns energy to a wearer. The relatively wide and horizontal elevated portions 34 of central walls 28 renders the central portion less stiff than tubular portion 24. At the widest part of the cushion 10, which is shaped for a heel, central portion 26 reaches a maximum width 74 that is greater than about 50% of the maximum width 84 of cushion 10 from the medial edge of the medial tubular portion 18 to the lateral edge of the lateral tubular portion 20. One of the medial and lateral tubular portions 18 and 20 is at least about 15% as wide as central portion 26 where cushion 10 is widest. Central and tubular portions 26 and 24 have substantially the same vertical height 72.
While the cushion described above exhibits satisfactory shock absorbing characteristics, there exists a need for an improved cushion that provides comparable to superior shock absorbing qualities at a reduced weight.